Fuse



July 315 1934- J. H. HANsoN Er A1, 1,968,763

FUSE

Filed March 14, 1955 INVENTORS THEIR ATTORNEYS Patented July 31, 1934 FUSE John H. Hanson and William E. Underwood,

Chicago, Ill.

Application March 14, 1933, serial No.Y 660,750

claims.

This invention relates to certain novel improvements in a fuse.`

We are aware of the fact that there are many types of renewable cartridge fuses known. In general these prior art fuses comprise a single cartridge or shell of fibrous or other insulating shell, a renewable fusible strip arranged in the shell, metal reeniorcing rings in the ends of the shell, and metal capsv closing the endsl of the 1b'. shell and rings and contacting with the fuse strip. Experience and experimentation with renewable fuses of this type have, however, taught us that they are unsatisfactoryA and unsafe, for

a number of reasons, among which are: When thefuse strip in a fuse of this type blows or melts the electric arc formed during the melting of the fuse strip fuses the metal closure and contact caps at the ends of the shell to the reenforcing rings or bushings, making it very I diiiicult, and often impossible, to remove the elosure caps to replace the fuse strip, and thus necessitating that the cartridge be discarded.

Moreover, the electric arc and the heat formed when a fusestrip .melts pulverizes the metal fuse I strip. As la series` of fuse strips are successively used up and fusedyin the same shella film of metal gradually accumulates on the inner surface of the shell, from end to end of the same, and this nlm .contacting with themetal rings, caps, or closure members usually arranged at the ends of the shell' forms a conductor that destroys or negatives ythe circuit andV ie protection afforded by `the fuse strip in the shell. ThisV is because of the fact that even if the fuse strip melts, due Vto ashort or other disturbance in the circuit, the circuit is still very apt to be kept closed by, theA said metallic lm formed on the inner side of the shell, as aforementionedby the successive fusing `of metal fuse strips which may be from time to time replaced in the same shell. For these and other reasons single shell renewal 'cartridge fuses have in general been refused approval b y the Afire insurance underwritersv and for this reason have, never come into general use.

, Objects of our invention, therefore are: to provide" a renewable cartridge fuse which overcomes the aforementioned and other defects in the prior art renewable cartridge fuses; which is positive and'reliablein use; which will meet with the 'approval of -the iire insurance underwriters; and to provide a double shell cartridge fuse having an inner replaceable rell cartridge in which the fuse strip is disposed, and which rei-lll cartridge may be taken outof the outer shell and discarded, aftereach successive fuse strip melts, and

replaced by anew reiill cartridgeLtherebypref-K.

venting the accumulation of 'a metallic iilm the inner` surface of the outer shell.

Other objects will appear hereinafter;l The invention consists in the novel combination and arrangement of parts to be,hereinaiter described and claimed.

The invention will be best understoodlby ref--` erence tothe accompanying drawing, showingthey preferrediorm of construction and in which:4

Fig. l1 is a perspective View of a preferredgform,

of the new fuse;

Fig. 2 is a longitudinal sectional View of the:

new fuse on line 2 2 in Fig. 1f;

Fig. 3 is a longitudinal sectional View ofxthe. new fuse on line 3-3 in Fig. 2;

Fig. 4 is a transverse sectional View on linee-4,

in Fig. 3;

Fig. 5 is a perspective detail view of a preferred form of the new fuse showing the parts disassembled; and.

Fig. 6 is alongitudinal sectionalA view of a.

slightly modified formof the new fuse.'

The new fuse is indicated generally at10'in the drawing and comprises a double shell'consisting of an outer insulating or non-conductive shell 11 and an ,innerJ .insulating or non-conductive. shell 12, both vof whichshells may be made-of' liber or other suitable non-conductive material.

The fusible strip 13 is arranged in the inner` and replaceable shell 12 and has end portionsi15" extended out through the openends of the inner shell 12. These end portions 15 are bent over bullet or wedge-shaped closure members 14; One of these wedge-shaped closure members'is ar-L rangedin and acts as a closure for each open end of the inner shell 12; These closure members 14 maybe madeof metal, such as brass, for example, or other material but they are preierablyfmade of a non-conductive or in'sulating'materi'al', gipreferred form of which is porcelain; The end portions 15 of the fuse striplare electrically connected to contact members 17 by means of electrically conductive closure members in the rform of metal caps 16. These caps 16 are threaded into the metal contact members 17 which are in the form of bushings that are threaded onto the end portions Vof the `outer shell 11. In the form of the fuse shown in Figs. 1 to 5, inclusive, both ends ofthe outer shell are. closed by closure cap 16 threaded into ther contact bushings 17; vwhile in the modied form of the fuse shown in Figv. 6 one end of the outer shell l1 is closed by a contact bushing-18 that is similar to the contact bushings 1'7 but has an integral portion 19 closing one end of the outer shell; the portion 19 taking the place of one of the caps 16. Otherwise the two forms of the new fuse are the same.

5 Each of the closure members 14 has a flat side or face extending longitudinally thereof so as to provide an air vent in each end of the inner shell 12 for the escape of the heated'gases and vapors through the ends of the inner shell when the fuse strip 13 melts.

'Ihe refill cartridge, consisting of the inner shell 12, the fuse strip 13, and the closure mem-J bers 14, may be manufactured as a separate unit or article of manufacture and sold as a rell for the outer shell 11; the rell cartridge being vmade by assembling the fuse strip 13 and the closure members 14, as shown, with the end portions 15 of the fuse strip angled over the outer ends of the closure members 14. 'I'he rell cartridgei12-13.

' 14 may then be inserted into the outer shell or? cartridge 11, by vvremoving one of the closure members or caps 16,'Whereupon the said cap 16 may be replaced by'threading the same into its bushing orcontact member' 1'7 'thereby forcing bothfangled end portions l15 of the fuse against the metal closure caps 16. In this manner a positive, efficient electrical connection is effected between the fuse strips 13 andthe contact rings or n bushings 17 by way of the closurecaps 16.

When the fuse strip 13 is melted or blows, one oftheclosure caps 16 may be removed and the inner cartridge 12-13--14 may then be removed from the outer shell 11. The used inner cartridge 41 12-13--14 may then be discarded and a new refill J cartridge y12---13--14 be placed in the outer shell 11, and the whole assembled for use as shown; for, a new fuse strip`13 may be placed in the shell 12 and the closure members 14 replaced to forma new reiill cartridge, if desired. How- 403 ever, destruction of the used inner shell 12 and substitution of a new refill cartridge, or` at least a: newinner shell 12, is desired since this does away with the danger incident to repeated use of the inner shell 12, namely, that a nlm of metal 451i may accumulate on the inner surface of the inner shell 12, if the same is'used repeatedly, and thus negative, in the aforementioned'manner, the proltection'ai'forded by the fuse strip 13.

The. closure members 14, being made of non- 5'0'? conductive material, the arc and'heatincident to the fusing of the strip 13 do not fuse these closure members 14 to the metal closure caps 16, nor to the contact rings 1'?, and'v hence the .inner cartridge 12-13-14 may be readily removed from the outer shell and replaced; thus` obviating a diiculty experienced in the use of the prior art single shell cartridge fuses, namely, that thearc and heat incident to the melting of the fuse commonly caused the lclosure members at the ends of of the singlershell to fuse to the contact `rings so that the shell could not beopened toreplace the fuse` strip... A

We have shown a preferred structure for effect--l ing an eilicient electrical connectionbetween the endV portions 15.0f the fuse strip y13 andthe contact ,membersll' but 'we are aware that'thisarrangement maybeyaried and wev contemplate such variationsinthe lappended claims; the invention beingjclearly indicated in the claims as residing broadly in the rei-lll cartridge 12-'13-14 aridjinjthe combination or assembly `of the rell ,cartridge 12-13-4-14 with the outer shell and contact members; rather than in any one detail of T i 'the structure shown. 'I5 Having thus described our invention what we l,first-nfientioned tubular member, and end caps having threaded connections with the second tubular member for closing the ends of the same. 2. In a renewable fuse, a tubular member, a

fuse strip positioned in said tubular member and having itsV vends projecting beyond the ends of the tubular member, a plug pressed into each end of the tubular member and having a iiange, said fuse strip being pinched between the plugs and the inner wall of said tubular member and between the ends of the tubular member andsaid flanges, each plug being provided With'a'iiat side, a second tubular member enclosing the mst-mentioned tubular member, and end caps having threaded connections with the second tubular member for closing the ends of the same, one of saidv caps being provided with a plug hav? ing threaded relation therewith. l l

3. A renewable fuse comprising an outer shell having a contact bushing attached to each end, one of said contact bushings being a cap arranged to close its respective end of the shell and the other bushing being provided with a threaded 110 opening; an insert comprising an inner shell, a fuse strip arrangedV within said inner shell and having its ends projecting from the ends of said inner shell, a plug pressed into each end of the shell for supportingthe fuse strip, the ends of 115 the fuse strip being positioned adjacent the exterior ends of said plugs; said insert being of smaller proportions than the outer shell and arranged within the latter with one end engaging said closed contact bushing, and a screw plug cooperating with said threaded opening for engaging the opposite end of the insert, to iirmly press the ends of the fuse strip against said screw plug and said closed contact bushing.

4. A fuse comprising a tubular shell having a contact member connected with one end and arranged to close the same, a contact member connected with the opposite end and having a threaded opening, a rigid insert comprising in part a fuse strip positioned within said tubular shell, one end of the insert bearing against said first named contact member, to position the fuse strip in electrical contact with the Lcontact member, and a threaded plug positioned within the opening in the second-mentioned contact member and in electrical contact with the other end of the fuse strip, said threaded plug being arranged to apply endwise pressure to the insert.

5. A fuse comprising a tubular shell having a contact ferrule arranged about each of its ends, each ferrule being provided with interior` threads; an insert comprising an inner tube having a. fuse strip extending therethrough and plugs pressed into its open ends, the ends of the fuse strip being` bent over the exposed ends ofsaid plugs; said insert being of smaller proportions than said tubular shell and arranged within the latter, and a threaded plug screwed into each of the ferrules for establishing electrical contact be- 150 tween the fuse strip and the ferrules, said plugs applying endwise pressure to the insert.

6. A fuse comprising a tubular shell having a contact ferrule arranged about each of its ends, each ferrule being provided with a threaded opening; an insert comprising an inner tube having a fuse strip extending therethrough and plugs pressed into its open ends, the ends of the fuse strip being bent over the exposed ends of said plugs; said insert being of smaller proportions than said tubular shell and arranged within the latter, and a threaded closure plug screwed into each of the threaded openings in the ferrules for establishing electrical contact between the fuse strip and the ferrules, said closure plugs applying endwise pressure to the insert, at least one of said first-named plugs having a cut-away portion to provide a vent opening communicating with the interior of the inner tube, at least one of said closure plugs having an opening cooperating with said cut-away portion to provide a vent communicating with the atmosphere.

7. A fuse comprising a tubular shell having a contact member connected with one end and arranged to provide an abutment projecting over one open end of the shell, a contact member connected with the opposite end of the tubular shell and having an opening, a rigid insert having a fuse strip associated therewith, the ends of the fuse strip projecting beyond the ends of the insert, said insert being of non-conductive material and having end abutments, the ends of the fuse strip being bent to lie adjacent said end abutments, one of the bent ends of the fuse strip bearing against the abutment part of said first-named contact member, and a plug of conductive material adjustably positioned within the opening in the second-named contact member and in electrical contact with the opposite bent end of the fuse strip, said plug being arranged to apply endwise pressure to the insert.

8. A fuse comprising a tubular shell having a contact ferrule arranged about each of its ends, one of said ferrules providing an abutment, the other of said ferrules being provided with a threaded opening, an insert comprising an inner tube having a fuse strip extending therethrough with its ends projecting beyond the inner tube, a plug structure positioned within the inner tube to provide abutting surfaces, said inner tube and said plug structure being made of non-conducting material, the ends of said fuse strip being bent to lie over the said abutting surfaces, said inner tube being smaller in diameter than said threaded opening for insertion therethrough, one of the bent ends of said fuse strip bearing against the abutment part of said one ferrule, to establish electrical contact between the ferrule and the fuse strip, and a threaded member of conductive material screwed into said threaded opening in the other of said ferrules, to establish electrical contact between the other bent end of the fuse strip and the last-mentioned ferrule, said threaded member being arranged for applying enclwise pressure to the insert, to pinch bent ends of the fuse strip between said plug structure and the threaded member and said abutment.

JOHN H. HANSON. WILLIAM E. UNDERWOOD. 

